Selective etch for silicon films

ABSTRACT

A method of etching patterned heterogeneous silicon-containing structures is described and includes a remote plasma etch with inverted selectivity compared to existing remote plasma etches. The methods may be used to conformally trim polysilicon while removing little or no silicon oxide. More generally, silicon-containing films containing less oxygen are removed more rapidly than silicon-containing films which contain more oxygen. Other exemplary applications include trimming silicon carbon nitride films while essentially retaining silicon oxycarbide. Applications such as these are enabled by the methods presented herein and enable new process flows. These process flows are expected to become desirable for a variety of finer linewidth structures. Methods contained herein may also be used to etch silicon-containing films faster than nitrogen-and-silicon containing films having a greater concentration of nitrogen.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/088,930, filed Apr. 18, 2011, which claims the benefit of U.S.Provisional Patent Application No. 61/348,920, filed May 27, 2010, theentire disclosure of which is incorporated by reference herein for allpurposes.

BACKGROUND OF THE INVENTION

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e.g. apattern transfer process proceed. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits and processes, etch processes have been developedwith a selectivity towards a variety of materials.

A Siconi™ etch is a remote plasma assisted dry etch process whichinvolves the simultaneous exposure of a substrate to H₂, NF₃ and NH₃plasma by-products. Remote plasma excitation of the hydrogen andfluorine species allows plasma-damage-free substrate processing. TheSiconi™ etch is largely conformal and selective towards silicon oxidelayers but does not readily etch silicon regardless of whether thesilicon is amorphous, crystalline or polycrystalline. The selectivityprovides advantages for applications such as shallow trench isolation(STI) and inter-layer dielectric (ILD) recess formation. The Siconi™process produces solid by-products which grow on the surface of thesubstrate as substrate material is removed. The solid by-products aresubsequently removed via sublimation when the temperature of thesubstrate is raised.

To date, remote plasma etches (such as Siconi™) have been limited toselectivity towards silicon oxide. Methods are needed to expand therange of possible selectivities for remote plasma etch processes.

BRIEF SUMMARY OF THE INVENTION

A method of etching patterned heterogeneous silicon-containingstructures is described and includes a remote plasma etch with invertedselectivity compared to existing remote plasma etches. The methods maybe used to conformally trim polysilicon while removing little or nosilicon oxide. More generally, silicon-containing films containing lessoxygen are removed more rapidly than silicon-containing films whichcontain more oxygen. Other exemplary applications include trimmingsilicon carbon nitride films while essentially retaining siliconoxycarbide. Applications such as these are enabled by the methodspresented herein and enable new process flows. These process flows areexpected to become desirable for a variety of finer linewidthstructures. Methods contained herein may also be used to etchsilicon-containing films faster than nitrogen-and-silicon containingfilms having a greater concentration of nitrogen.

Embodiments of the invention include methods of etching patternedsubstrate in a substrate processing region of a substrate processingchamber. The patterned substrate has an exposedoxygen-and-silicon-containing region and an exposed silicon-containingregion which contains less oxygen than the oxygen-and-silicon-containingregion. The method includes flowing a fluorine-containing precursor intoa remote plasma region fluidly coupled to the substrate processingregion while forming a plasma in the first plasma region to produceplasma effluents. The method further includes etching thesilicon-containing region faster than the oxygen-and-silicon-containingregion by flowing the plasma effluents into the substrate processingregion.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedembodiments may be realized by reference to the remaining portions ofthe specification and the drawings.

FIG. 1 is a flow chart of a silicon selective etch process according todisclosed embodiments.

FIGS. 2A-2B are schematics before and after a silicon selective etchprocess according to disclosed embodiments.

FIG. 3 is a plot indicating etch rates of silicon oxide, silicon nitrideand polysilicon during a silicon selective etch according to disclosedembodiments.

FIG. 4 is a flow chart of a selective etch process according todisclosed embodiments.

FIGS. 5A-5B are schematics before and after a selective etch processaccording to disclosed embodiments.

FIG. 6 is a plot indicating etch rates of silicon oxycarbide and siliconcarbon nitride during a selective etch according to disclosedembodiments.

FIG. 7 is a cross-sectional view of a processing chamber for performingetch processes according to disclosed embodiments.

FIG. 8 is a processing system for performing etch processes according todisclosed embodiments.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION OF THE INVENTION

A method of etching patterned heterogeneous silicon-containingstructures is described and includes a remote plasma etch with invertedselectivity compared to existing remote plasma etches. The methods maybe used to conformally trim polysilicon while removing little or nosilicon oxide. More generally, silicon-containing films containing lessoxygen are removed more rapidly than silicon-containing films whichcontain more oxygen. Other exemplary applications include trimmingsilicon carbon nitride films while essentially retaining siliconoxycarbide. Applications such as these are enabled by the methodspresented herein and enable new process flows. These process flows areexpected to become desirable for a variety of finer linewidthstructures. Methods contained herein may also be used to etchsilicon-containing films faster than nitrogen-and-silicon containingfilms having a greater concentration of nitrogen.

Siconi™ etch processes have used a hydrogen source of ammonia (NH₃) anda fluorine source of nitrogen trifluoride (NF₃) which together flowthrough a remote plasma system (RPS) and into a reaction region. Theflow rates of ammonia and nitrogen trifluoride are typically chosen suchthat the atomic flow rate of hydrogen is roughly twice that of fluorinein order to efficiently utilize the constituents of the two processgases. The presence of hydrogen and fluorine allows the formation ofsolid byproducts of (NH₄)₂SiF₆ at relatively low substrate temperatures.The solid byproducts are removed by raising the temperature of thesubstrate above the sublimation temperature. Siconi™ etch processesremove oxide films more rapidly than films devoid of oxygen. Theinventors have discovered that the selectivity can be inverted byreducing (or eliminating) the supply of hydrogen while retaining theflow of nitrogen trifluoride.

In order to better understand and appreciate the invention, reference isnow made to FIGS. 1 and 2 which are a flow chart of a oxide deselectiveetch process and a shallow trench isolation (STI) structure according todisclosed embodiments. Prior to the first operation, a gap is formed ina polysilicon adlayer 220-1 and an underlying silicon substrate 210. Thegap is filled with silicon oxide 230 to electrically isolate devices(not shown). The silicon oxide is polished such that the surface isroughly coplanar with the top of the polysilicon and the silicon oxideis trimmed back below the polysilicon to achieve the structure shown inFIG. 2. The process of FIG. 1 begins when the substrate is transferredinto a processing chamber (operation 110). Note that regions of siliconoxide 230 and polysilicon 220 are exposed on the surface of thesubstrate.

A flow of nitrogen trifluoride is initiated into a plasma regionseparate from the processing region (operation 120). Other sources offluorine may be used to augment or replace the nitrogen trifluoride. Inembodiments, the fluorine-containing precursor comprises at least oneprecursor selected from the group consisting of nitrogen trifluoride,diatomic fluorine, monatomic fluorine and fluorine-substitutedhydrocarbons. The separate plasma region may be referred to as a remoteplasma region herein and may be within a distinct module from theprocessing chamber or a compartment within the processing chamber. Aflow of ammonia may or may not be present into the remote plasma regionduring this operation. When included, the hydrogen-containing precursorcomprises at least one precursor selected from the group consisting ofatomic hydrogen, molecular hydrogen, ammonia, a hydrocarbon and anincompletely halogen-substituted hydrocarbon. The flows of nitrogentrifluoride and optional ammonia may be selected such that thefluorine-to-hydrogen atomic flow ratio is greater than one of 2:1, 5:1or 10:1. Products from the remote plasma (plasma effluents) are flowedinto the processing region and allowed to interact with the patternedsubstrate surface (operation 125). The patterned layer is selectivelyetched (operation 130) such that the polysilicon adlayer is conformallytrimmed while the silicon oxide gapfill 230 is etched more slowly indisclosed embodiments. The etch rate of the polysilicon may be greaterthan five or ten times the etch rate of the silicon oxide gapfilldepending on the ratio of the flow of fluorine to the flow of hydrogen.The flows of the gases are then stopped (operation 135) and thesubstrate is removed from the processing region (operation 145). Thepolysilicon may be trimmed by between 1 nm and 15 nm in disclosedembodiments. Including a significant flow of oxygen into the remoteplasma region (and therefore in the plasma effluent flow) is notrecommended since the silicon may be oxidized thwarting the desirableetch selectivity towards silicon. The plasma region and substrateprocessing region are devoid or essentially devoid of oxygen during theetch process, according to embodiments of the invention.

FIG. 3 is a plot of etch quantities after a timed etch such as that usedto trim the polysilicon adlayer 220 of FIG. 2. Note that a Siconi™,having about twice the atomic concentration of hydrogen as compared withfluorine, results in silicon oxide removal at a significantly greaterrate than polysilicon. The selectivity inverts as the ratio of hydrogento fluorine is reduced. Polysilicon and silicon oxide are removed atroughly the same rate when equal parts of hydrogen and fluorine aredelivered to the remote plasma region. Below a ratio of 1:1hydrogen:fluorine, the etch rate of polysilicon exceeds that of siliconoxide. Essentially no hydrogen is flowed to the remote plasma region, inembodiments, which results in an etch selectivity greater than 10:1polysilicon:silicon oxide. The technique may also be applied to a gap ina silicon substrate without a polysilicon adlayer, in embodiments, andthe oxide deselective etch would remove silicon at a greater rate thanthe silicon oxide gapfill.

The selective etch represented by FIGS. 1-3 was described in conjunctionwith a shallow-trench isolation application. A variety of otherapplications will benefit from this silicon-selective etch. For example,this selective etch may be used to trim the fin of a finFET structurewithout removing a detrimental quantity of exposed oxygen-containingmaterial such as silicon oxide. A finFET contains a vertical protrusionof single crystalline silicon whose thickness impacts deviceperformance. Single crystalline silicon etches at a similar rate topolysilicon when processed with the remote plasma selective etchdescribed herein. A wide variety of alternative geometries to the devicestructures described herein are expected to emerge and will benefit fromthe oxide deselective etch.

The utility of the remote plasma etch described herein is not limited tosystems including patterned silicon and silicon oxide. FIG. 4 is a flowchart of a selective etch which removes silicon carbon nitride (SiCN)faster than silicon oxy-carbide (SiOC). In embodiments the SiCN consistsessentially of silicon, carbon and nitrogen. Similarly, the SiOC mayconsist essentially of silicon, carbon and oxygen. FIGS. 5A-5B areschematics of an exemplary application before and after the selectiveetch. The exemplary application involves formation of an inter-metaldielectric layer. An underlying copper layer 550 has a silicon carbonnitride (SiCN) 560-1 formed above it to prevent the diffusion ofcontaminants from overlying low-K film 570. A suitable SiCN film 560-1is Blok™ and a suitable low-K film 570 is Black Diamond, each of whichis available from Applied Materials, Santa Clara, Calif. The low-K film570 is formed above the layer of SiCN 560-1 and patterned with an oxideselective etch to form the trench shown in FIG. 5A. The trench willlater be filled with metal to form a conducting link between differentmetal layers. Before an ohmic contact can be made, however, thedielectric SiCN must first be removed.

The process of FIG. 4 begins when the patterned substrate is transferredinto a processing chamber (operation 410). A flow of nitrogentrifluoride is initiated into the remote plasma region (operation 420).The remote plasma region may be essentially devoid of hydrogen or havelesser flows of hydrogen as described previously with reference to FIGS.1-2. Hydrogen is impossible to completely eliminate from a vacuum systemand “essentially devoid” of hydrogen is used to accommodate reasonabletolerances. Plasma effluents are flowed into the processing region andallowed to interact with the patterned substrate surface (operation425). The patterned layer is selectively etched (operation 430) suchthat the silicon carbon nitride layer is preferentially removed relativeto the silicon oxy-carbide. The selective etch continues until theportion of the SiCN is removed from the bottom of the trench to allow asubsequent layer of metal to contact the newly exposed carbon surface.The flows of the precursors are stopped (operation 435) and thesubstrate is removed from the processing region (operation 445). TheSiCN film 560-2 following the selective etch is shown in FIG. 5B.

FIG. 6 is a plot indicating etch rates of silicon oxycarbide and siliconcarbon nitride during an oxide deselective etch according to disclosedembodiments. The curves show the dependence of etch rate on the partialpressure of nitrogen trifluoride in the substrate processing region. Inaddition to being dependent on the hydrogen:fluorine atomic flow ratioas indicated previously, the selectivity is further dependent on theconcentration of nitrogen trifluoride in the vicinity of the patternedsubstrate. Lower partial pressures enable an increase in the selectivityof SiCN over SiOC which is preferred in the exemplary application. Belowabout 50 mTorr partial pressure nitrogen trifluoride, the etch rate ofboth SiCN and SiOC reduce as the partial pressure is reduced. The rateof reduction is faster for the SiOC which allows the selectivity towardetching SiCN to be increased. The partial pressure of nitrogentrifluoride is below 50 mTorr, 30 mTorr or 20 mTorr in differentembodiments.

The oxide deselective etch described herein etches materials which areessentially devoid of oxygen faster than oxygen-and-silicon containingfilms. It is noteworthy that a small amount of oxygen is often presentin SiCN and polysilicon even when inclusion of oxygen is not intended.Furthermore, common measurement techniques used to determine elementalcomposition may over-report the presence of oxygen due to atmosphericcontamination during sample preparation and measurement. Describing amaterial as “essentially devoid of oxygen” or “oxygen-free” accommodatesthese as acceptable tolerances. Even more generally, asilicon-containing film having less oxygen will etch more rapidly than asilicon-containing film having more oxygen. In embodiments, thesilicon-containing film may consist essentially of silicon either inamorphous, crystalline or polycrystalline form. Similarly, theoxygen-and-silicon-containing film may consist essentially of SiO₂. Theoxide deselective etch may still have utility as long as both films haveexposed surfaces since each will etch at a different rate. The etch rateof an exposed silicon-containing region may be greater than an etch rateof an exposed oxygen-and-silicon-containing region by a multiplicativefactor greater than five in embodiments of the invention.

Oxide deselective etches have been described thus far. The methodsdescribed herein may be used to selectively etch silicon faster thansilicon nitride as shown in FIG. 3. The selectivity is not as pronouncedas is the case for silicon etch selectivity over silicon oxide. Thedifference can still be helpful in a variety of process flows. Theseetch processes may be referred to herein as nitride deselective etchesand have the same process parameter embodiments described with referenceto oxide deselective etches. Analogously, the remote plasma region andthe substrate processing region may each be devoid or essentially devoidof nitrogen during these etch processes, according to embodiments of theinvention. Generally speaking, silicon-containing materials may beetched selectively compared to a nitrogen-and-silicon-containingmaterial having a greater nitrogen concentration than thesilicon-containing materials. The etch rate of an exposedsilicon-containing region may be greater than an etch rate of an exposednitrogen-and-silicon-containing material by a multiplicative factorgreater than 1.5 in embodiments of the invention. Silicon-containingfilms, such as silicon, may also be etched faster thannitrogen-oxygen-and-silicon-containing films.

Additional oxide deselective etch process parameters are disclosed inthe course of describing an exemplary processing system.

Exemplary Processing System

FIG. 7 is a partial cross sectional view showing an illustrativeprocessing chamber 700, in which, embodiments of the invention may becarried out. Generally, a hydrogen-containing precursor and afluorine-containing precursor may be introduced through one or moreapertures 751 into remote plasma region(s) 761-763 and excited by plasmapower source 746.

In one embodiment, the processing chamber 700 includes a chamber body712, a lid assembly 702, and a support assembly 710. The lid assembly702 is disposed at an upper end of the chamber body 712, and the supportassembly 710 is at least partially disposed within the chamber body 712.The processing chamber 700 and the associated hardware are preferablyformed from one or more process-compatible materials (e.g. aluminum,stainless steel, etc.).

The chamber body 712 includes a slit valve opening 760 formed in asidewall thereof to provide access to the interior of the processingchamber 700. The slit valve opening 760 is selectively opened and closedto allow access to the interior of the chamber body 712 by a waferhandling robot (not shown). In one embodiment, a wafer can betransported in and out of the processing chamber 700 through the slitvalve opening 760 to an adjacent transfer chamber and/or load-lockchamber, or another chamber within a cluster tool. An exemplary clustertool which may include processing chamber 700 is shown in FIG. 8.

In one or more embodiments, chamber body 712 includes a chamber bodychannel 713 for flowing a heat transfer fluid through chamber body 712.The heat transfer fluid can be a heating fluid or a coolant and is usedto control the temperature of chamber body 712 during processing andsubstrate transfer. Heating the chamber body 712 may help to preventunwanted condensation of the gas or byproducts on the chamber walls.Exemplary heat transfer fluids include water, ethylene glycol, or amixture thereof. An exemplary heat transfer fluid may also includenitrogen gas. Support assembly 710 may have a support assembly channel704 for flowing a heat transfer fluid through support assembly 710thereby affecting the substrate temperature.

The chamber body 712 can further include a liner 733 that surrounds thesupport assembly 710. The liner 733 is preferably removable forservicing and cleaning. The liner 733 can be made of a metal such asaluminum, or a ceramic material. However, the liner 733 can be anyprocess compatible material. The liner 733 can be bead blasted toincrease the adhesion of any material deposited thereon, therebypreventing flaking of material which results in contamination of theprocessing chamber 700. In one or more embodiments, the liner 733includes one or more apertures 735 and a pumping channel 729 formedtherein that is in fluid communication with a vacuum system. Theapertures 735 provide a flow path for gases into the pumping channel729, which provides an egress for the gases within the processingchamber 700.

The vacuum system can include a vacuum pump 725 and a throttle valve 727to regulate flow of gases through the processing chamber 700. The vacuumpump 725 is coupled to a vacuum port 731 disposed on the chamber body712 and therefore, in fluid communication with the pumping channel 729formed within the liner 733. The terms “gas” and “gases” are usedinterchangeably, unless otherwise noted, and refer to one or morereactants, catalysts, carrier, purge, cleaning, combinations thereof, aswell as any other fluid introduced into the chamber body 712. The term“precursor” is used to refer to any process gas which takes part in areaction to either remove or deposit material from a surface.

Apertures 735 allow the pumping channel 729 to be in fluid communicationwith a processing region 740 within the chamber body 712. The processingregion 740 is defined by a lower surface of the lid assembly 702 and anupper surface of the support assembly 710, and is surrounded by theliner 733. The apertures 735 may be uniformly sized and evenly spacedabout the liner 733. However, any number, position, size or shape ofapertures may be used, and each of those design parameters can varydepending on the desired flow pattern of gas across the substratereceiving surface as is discussed in more detail below. In addition, thesize, number and position of the apertures 735 are configured to achieveuniform flow of gases exiting the processing chamber 700. Further, theaperture size and location may be configured to provide rapid or highcapacity pumping to facilitate a rapid exhaust of gas from the chamber700. For example, the number and size of apertures 735 in closeproximity to the vacuum port 731 may be smaller than the size ofapertures 735 positioned farther away from the vacuum port 731.

A gas supply panel (not shown) is typically used to provide processgas(es) to the processing chamber 700 through one or more apertures 751.The particular gas or gases that are used depend upon the process orprocesses to be performed within the chamber 700. Illustrative gases caninclude, but are not limited to one or more precursors, reductants,catalysts, carriers, purge, cleaning, or any mixture or combinationthereof. Typically, the one or more gases introduced to the processingchamber 700 flow into plasma volume 761 through aperture(s) 751 in topplate 750. Alternatively or in combination, processing gases may beintroduced more directly through aperture(s) 752 into processing region740. Aperture(s) 752 bypass the remote plasma excitation and are usefulfor processes involving gases that do not require plasma excitation orprocesses which do not benefit from additional excitation of the gases.Electronically operated valves and/or flow control mechanisms (notshown) may be used to control the flow of gas from the gas supply intothe processing chamber 700. Depending on the process, any number ofgases can be delivered to the processing chamber 700, and can be mixedeither in the processing chamber 700 or before the gases are deliveredto the processing chamber 700.

The lid assembly 702 can further include an electrode 745 to generate aplasma of reactive species within the lid assembly 702. In oneembodiment, the electrode 745 is supported by top plate 750 and iselectrically isolated therefrom by inserting electrically isolatingring(s) 747 made from aluminum oxide or any other insulating and processcompatible material. In one or more embodiments, the electrode 745 iscoupled to a power source 746 while the rest of lid assembly 702 isconnected to ground. Accordingly, a plasma of one or more process gasescan be generated in remote plasma region composed of volumes 761, 762and/or 763 between electrode 745 and annular mounting flange 722. Inembodiments, annular mounting flange comprises or supports gas deliveryplate 720. For example, the plasma may be initiated and maintainedbetween electrode 745 and one or both blocker plates of blocker assembly730. Alternatively, the plasma can be struck and contained between theelectrode 745 and gas delivery plate 720, in the absence of blockerassembly 730. In either embodiment, the plasma is well confined orcontained within the lid assembly 702. Accordingly, the plasma is a“remote plasma” since no active plasma is in direct contact with thesubstrate disposed within the chamber body 712. As a result, plasmadamage to the substrate may be avoided since the plasma is separatedfrom the substrate surface.

A wide variety of power sources 746 are capable of activating thenitrogen-containing precursor (nitrogen trifluoride). For example, radiofrequency (RF), direct current (DC), or microwave (MW) based powerdischarge techniques may be used. The activation may also be generatedby a thermally based technique, a gas breakdown technique, a highintensity light source (e.g., UV energy), or exposure to an x-raysource. Alternatively, a remote activation source may be used, such as aremote plasma generator, to generate a plasma of reactive species whichare then delivered into the chamber 700. Exemplary remote plasmagenerators are available from vendors such as MKS Instruments, Inc. andAdvanced Energy Industries, Inc. In the exemplary processing system anRF power supply is coupled to electrode 745. A higher-power microwavepower source 746 is beneficial in the event that reactive oxygen willalso be produced using power source 746.

The temperatures of the process chamber body 712 and the substrate mayeach be controlled by flowing a heat transfer medium through chamberbody channel 713 and support assembly channel 704, respectively. Supportassembly channel 704 may be formed within support assembly 710 tofacilitate the transfer of thermal energy. Chamber body 712 and supportassembly 710 may be cooled or heated independently. For example, aheating fluid may be flown through one while a cooling fluid is flownthrough the other.

Other methods may be used to control the substrate temperature. Thesubstrate may be heated by heating the support assembly 710 (or aportion thereof, such as a pedestal) with a resistive heater or by someother means. In another configuration, gas delivery plate 720 may bemaintained at a temperature higher than the substrate and the substratecan be elevated in order to raise the substrate temperature. In thiscase the substrate is heated radiatively or by using a gas to conductheat from gas delivery plate 720 to the substrate. The substrate may beelevated by raising support assembly 710 or by employing lift pins.

During the etch processes described herein, chamber body 712 may bemaintained within an approximate temperature range of between 50° C. and80° C., between 55° C. and 75° C. or between 60° C. and 70° C. indifferent embodiments. During exposure to plasma effluents and/oroxidizing agents, the substrate may be maintained below about 100° C.,below about 65° C., between about 15° C. and about 50° C. or betweenabout 22° C. and about 40° C. in different embodiments. The substratemay also be held at elevated temperatures during the etch since theoxide deselective etch does not rely as heavily if at all on asublimation step. The substrate may be maintained above 70° C., above100° C. or above 130° C. in disclosed embodiments.

Plasma effluents include a variety of molecules, molecular fragments andionized species. During oxide deselective etching, plasma effluentsinclude fluorine radicals which react readily with exposedsilicon-containing material which lacks oxygen or possesses a smallamount of oxygen. Plasma effluents may react with a oxygen-freesilicon-containing layer to form SiF and H₂O vapor products which areremoved from processing region 740 by vacuum pump 725.

In embodiments, little or no hydrogen is introduced into the remoteplasma region. Under such conditions, little or no solid residue isproduced on the substrate surface and a sublimation step may be omitted.When a source of hydrogen is included, the substrate may be heated tosublimate solid residue etch by-products formed upon exposing thesubstrate to the plasma effluents. In embodiments, the gas deliveryplate 720 is heatable by incorporating heating element 770 within ornear gas delivery plate 720. The substrate may be heated by reducing thedistance between the substrate and the heated gas delivery plate. Thegas delivery plate 720 may be heated to between about 100° C. and 150°C., between about 110° C. and 140° C. or between about 120° C. and 130°C. in different embodiments. By reducing the separation between thesubstrate and the heated gas delivery plate, the substrate may be heatedto above about 75° C., above about 90° C., above about 100° C. orbetween about 115° C. and about 150° C. in different embodiments. When ahydrogen source is flowed along with a fluorine source, the heatradiated from gas delivery plate 720 to the substrate should be madesufficient to dissociate or sublimate solid (NH₄)₂SiF₆ from the oxideportions of the substrate into volatile SiF₄, NH₃ and HF products whichmay be pumped away from processing region 740.

Nitrogen trifluoride (or another fluorine-containing precursor) may beflowed into remote plasma volume 761 at rates between about 25 sccm andabout 200 sccm, between about 50 sccm and about 150 sccm or betweenabout 75 sccm and about 125 sccm in different embodiments. Ammonia (orhydrogen-containing precursors in general) may be flowed into remoteplasma volume 761 at rates below or about 20 sccm, below or about 15sccm, below or about 10 sccm, below or about 5 sccm or below or about 2sccm in different embodiments.

Combined flow rates of hydrogen-containing and fluorine-containingprecursors into the remote plasma region may account for 0.05% to about20% by volume of the overall gas mixture; the remainder being a carriergas. In one embodiment, a purge or carrier gas is first initiated intothe remote plasma region before those of the reactive gases to stabilizethe pressure within the remote plasma region.

Production of the plasma effluents occurs within volumes 761, 762 and/or763 by applying plasma power to electrode 745 relative to the rest oflid assembly 702. Plasma power can be a variety of frequencies or acombination of multiple frequencies. In the exemplary processing systemthe plasma is provided by RF power delivered to electrode 745. The RFpower may be between about 1 W and about 1000 W, between about 5 W andabout 600 W, between about 10 W and about 300 W or between about 20 Wand about 100 W in different embodiments. The RF frequency applied inthe exemplary processing system may be less than about 200 kHz, lessthan about 150 kHz, less than about 120 kHz or between about 50 kHz andabout 90 kHz in different embodiments.

Processing region 740 can be maintained at a variety of pressures duringthe flow of plasma effluents into processing region 740. The pressuremay be maintained between about 500 mTorr and about 30 Torr, betweenabout 1 Torr and about 10 Torr or between about 3 Torr and about 6 Torrin different embodiments. Lower pressures may also be used withinprocessing region 740. The pressure may be maintained below or about 500mTorr, below or about 250 mTorr, below or about 100 mTorr, below orabout 50 mTorr or below or about 20 mTorr in different embodiments.

The selectivity of the etch process may be enhanced by neutralizingcharged species generated in volumes 761-763 prior to flowing plasmaeffluents into the substrate processing region. Neutral reactiveradicals (molecular fragments) are still passed into the substrateprocessing region and react with the substrate to perform the selectiveetch process. To this end, the holes in the showerhead may be narrowedto increase the neutralizing collisions as effluents migrate toward thesubstrate processing region. A separate showerhead may also be includedin the path of the plasma effluents to suppress the flow of ions intothe substrate processing region. The separate showerhead may be referredto as an ion suppressor (not shown). These neutral (uncharged) speciesmay still include highly reactive species that are transported with lessreactive carrier gas through the holes. The flow of ionized effluentsinto the substrate processing region may be reduced to below the flow ofneutral species on a per molecular fragment basis. The flow may also bebelow 10% of the neutral species or may be essentially eliminated, indisclosed embodiments. Controlling the amount of ionic species passinginto the substrate processing region provides increased control over thegas mixture brought into contact with the underlying wafer substrate,increasing control of the selectivity of the etch process.

A plurality of holes in the ion suppressor and/or the showerhead may beconfigured to control the passage of the activated gas (i.e., the ionic,radical, and/or neutral species) into the substrate processing region.For example, the aspect ratio of the holes (i.e., the hole diameter tolength) and/or the geometry of the holes may be controlled so that theflow of ionically-charged species in the activated gas passing into thesubstrate processing region is reduced. The holes may include a taperedportion that faces the remote plasma region (volumes 761, 762 and/or763). The taper may serve to allow a substantial number of effluentsinto the hole but force a large percentage of the effluents to undergoneutralizing collisions prior to entering the substrate processingregion. An adjustable electrical bias may also be applied to the ionsuppressor and/or showerhead as an additional means to control the flowof ionic species through the suppressor.

In one or more embodiments, the processing chamber 700 can be integratedinto a variety of multi-processing platforms, including the Producer™GT, Centura™ AP and Endura™ platforms available from Applied Materials,Inc. located in Santa Clara, Calif. Such a processing platform iscapable of performing several processing operations without breakingvacuum.

FIG. 8 is a schematic top-view diagram of an illustrative multi-chamberprocessing system 800. The system 800 can include one or more load lockchambers 802, 804 for transferring of substrates into and out of thesystem 800. Typically, since the system 800 is under vacuum, the loadlock chambers 802, 804 may “pump down” the substrates introduced intothe system 800. A first robot 810 may transfer the substrates betweenthe load lock chambers 802, 804, and a first set of one or moresubstrate processing chambers 812, 814, 816, 818 (four are shown). Eachprocessing chamber 812, 814, 816, 818, can be outfitted to perform anumber of substrate processing operations including the dry etchprocesses described herein in addition to cyclical layer deposition(CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD),physical vapor deposition (PVD), etch, pre-clean, degas, orientation andother substrate processes.

The first robot 810 can also transfer substrates to/from one or moretransfer chambers 822, 824. The transfer chambers 822, 824 can be usedto maintain ultrahigh vacuum conditions while allowing substrates to betransferred within the system 800. A second robot 830 can transfer thesubstrates between the transfer chambers 822, 824 and a second set ofone or more processing chambers 832, 834, 836, 838. Similar toprocessing chambers 812, 814, 816, 818, the processing chambers 832,834, 836, 838 can be outfitted to perform a variety of substrateprocessing operations including the dry etch processes described hereinin addition to cyclical layer deposition (CLD), atomic layer deposition(ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD),etch, pre-clean, degas, and orientation, for example. Any of thesubstrate processing chambers 812, 814, 816, 818, 832, 834, 836, 838 maybe removed from the system 800 if not necessary for a particular processto be performed by the system 800.

System controller 857 is used to control motors, valves, flowcontrollers, power supplies and other functions required to carry outprocess recipes described herein. System controller 857 may rely onfeedback from optical sensors to determine and adjust the position ofmovable mechanical assemblies. Mechanical assemblies may include therobot, throttle valves and susceptors which are moved by motors underthe control of system controller 857.

In an exemplary embodiment, system controller 857 includes a hard diskdrive (memory), USB ports, a floppy disk drive and a processor. Systemcontroller 857 includes analog and digital input/output boards,interface boards and stepper motor controller boards. Various parts ofmulti-chamber processing system 800 which contains processing chamber800 are controlled by system controller 857. The system controllerexecutes system control software in the form of a computer programstored on computer-readable medium such as a hard disk, a floppy disk ora flash memory thumb drive. Other types of memory can also be used. Thecomputer program includes sets of instructions that dictate the timing,mixture of gases, chamber pressure, chamber temperature, RF powerlevels, susceptor position, and other parameters of a particularprocess.

A process for etching, depositing or otherwise processing a film on asubstrate or a process for cleaning chamber can be implemented using acomputer program product that is executed by the controller. Thecomputer program code can be written in any conventional computerreadable programming language: for example, 68000 assembly language, C,C++, Pascal, Fortran or others. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is compiled, and the resultant compiler code is then linkedwith an object code of precompiled Microsoft Windows® library routines.To execute the linked, compiled object code the system user invokes theobject code, causing the computer system to load the code in memory. TheCPU then reads and executes the code to perform the tasks identified inthe program.

The interface between a user and the controller may be via atouch-sensitive monitor and may also include a mouse and keyboard. Inone embodiment two monitors are used, one mounted in the clean room wallfor the operators and the other behind the wall for the servicetechnicians. The two monitors may simultaneously display the sameinformation, in which case only one is configured to accept input at atime. To select a particular screen or function, the operator touches adesignated area on the display screen with a finger or the mouse. Thetouched area changes its highlighted color, or a new menu or screen isdisplayed, confirming the operator's selection.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The support substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. A gas in an “excited state”describes a gas wherein at least some of the gas molecules are invibrationally-excited, dissociated and/or ionized states. A gas may be acombination of two or more gases. “Silicon oxide” is predominantly SiO₂but may include concentrations of other elemental constituents such asnitrogen, hydrogen, carbon and the like. The terms “gap” and “trench”are used throughout with no implication that the etched geometry has alarge horizontal aspect ratio. Viewed from above the surface, thesestructures may appear circular, oval, polygonal, rectangular, or avariety of other shapes. As used herein, a conformal etch process refersto a generally uniform removal of material on a surface in the sameshape as the surface, i.e., the surface of the etched layer and thepre-etch surface are generally parallel. A person having ordinary skillin the art will recognize that the etched interface likely cannot be100% conformal and thus the term “generally” allows for acceptabletolerances.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well known processesand elements have not been described in order to avoid unnecessarilyobscuring the present invention. Accordingly, the above descriptionshould not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A method of etching patterned substrate in asubstrate processing region of a substrate processing chamber, whereinthe patterned substrate has an exposed oxygen-and-silicon-containingregion and an exposed silicon-containing region which contains lessoxygen than the oxygen-and-silicon-containing region, the methodcomprising: flowing a fluorine-containing precursor into a remote plasmaregion fluidly coupled to the substrate processing region while forminga plasma in the first plasma region to produce plasma effluents; andetching the silicon-containing region faster than theoxygen-and-silicon-containing region by flowing the plasma effluentsinto the substrate processing region, wherein the etching is performedwhile maintaining a partial pressure of the fluorine-containingprecursor below about 100 mTorr.
 2. The method of claim 1 wherein anetch rate of the exposed silicon-containing region is greater than anetch rate of the exposed oxygen-and-silicon-containing region by amultiplicative factor greater than
 5. 3. The method of claim 1 whereinthe exposed silicon-containing region is essentially devoid of oxygen.4. The method of claim 1 wherein the exposed silicon-containing regionconsists essentially of silicon.
 5. The method of claim 1 wherein theexposed oxygen-and-silicon-containing region consists essentially ofSiO2.
 6. The method of claim 1 wherein the exposed silicon-containingregion is polysilicon, the exposed oxygen-and-silicon-containing regionis SiO2 and the polysilicon is trimmed by between 1 nm and 15 nm.
 7. Themethod of claim 1 wherein the exposed silicon-containing region consistsessentially of silicon, carbon and nitrogen.
 8. The method of claim 1wherein the exposed oxygen-and-silicon-containing region consistsessentially of silicon, carbon and oxygen.
 9. The method of claim 1wherein the exposed silicon-containing region is SiCN, the exposedoxygen-and-silicon-containing region is SiOC and the SiCN is removedfrom the base of a trench formed in the SiOC.
 10. The method of claim 1wherein the fluorine-containing precursor comprises at least oneprecursor selected from the group consisting of nitrogen trifluoride,diatomic fluorine, monatomic fluorine and fluorine-substitutedhydrocarbons.
 11. The method of claim 1 wherein the plasma effluentspossess an atomic ratio of fluorine-to-hydrogen which is greater than5:1.
 12. The method of claim 1 wherein essentially no ionized speciesare present in the plasma effluents within the substrate processingregion to increase the etch selectivity of the silicon-containingregion.
 13. A method of etching patterned substrate in a substrateprocessing region of a substrate processing chamber, wherein thepatterned substrate has an exposed nitrogen-and-silicon-containingregion and an exposed silicon-containing region which contains lessnitrogen than the nitrogen-and-silicon-containing region, the methodcomprising: flowing a fluorine-containing precursor into a remote plasmaregion fluidly coupled to the substrate processing region while forminga plasma in the first plasma region to produce plasma effluents; andetching the silicon-containing region faster than thenitrogen-and-silicon-containing region by flowing the plasma effluentsinto the substrate processing region, wherein the etching is performedwhile maintaining a partial pressure of the fluorine-containingprecursor below about 100 mTorr.
 14. The method of claim 13 wherein anetch rate of the exposed silicon-containing region is greater than anetch rate of the exposed nitrogen-and-silicon-containing region by amultiplicative factor greater than 1.5.
 15. The method of claim 13wherein the exposed silicon-containing region is essentially devoid ofnitrogen.
 16. The method of claim 13 wherein the exposedsilicon-containing region consists essentially of silicon.
 17. Themethod of claim 13 wherein the exposed nitrogen-and-silicon-containingregion consists essentially of silicon nitride.
 18. The method of claim13 wherein the fluorine-containing precursor comprises at least oneprecursor selected from the group consisting of nitrogen trifluoride,diatomic fluorine, monatomic fluorine and fluorine-substitutedhydrocarbons.
 19. The method of claim 13 wherein the fluorine-containingprecursor and the plasma effluents are essentially devoid of hydrogen.20. The method of claim 13 wherein the plasma effluents possess anatomic ratio of fluorine-to-hydrogen which is greater than 5:1.